1. Field of the Invention
The present invention relates to a plant-cultivating artificial material, and a process for producing the same.
2. Description of the Related Art
Conventionally, there have been used various fertilizer components for promoting growth of plants. For example, bone meal has been added as a fertilizer in soil, containing calcium phosphate as a major component Although calcium phosphate constituting the bone meal corresponding to the fertilizer, is hardly dissolved by water; it can be dissolved by organic adds such as root acids secreted from roots of plants. Thus, such calcium phosphate comes to be absorbed into the roots of the plants together with water and other components included in soil.
Although bone meal is added in soil, the bone meal component dissolved by the organic acid easily flows together with water, such as rain water. Accordingly, water containing the bone meal component can easily escape from roots of plants. Thus, the above-described conventional technique does not always provide a sufficient effect of promoting growth of plants by addition of bone meal.
The present invention has been conceived in view of the above circumstances. It is an object of the present invention to provide a plant-cultivating artificial material and a process for producing the plant-cultivating artificial material which can promote growth of plants by holding of a bone material component or calcium phosphate.
In a first aspect of the present invention, a plant-cultivating artificial material comprises: (1) a porous sintered body containing at least one of silica and alumina as a major component; and (2) a substance mainly composed of a bone material component or calcium phosphate being held in the porous sintered body.
In the first aspect of the present invention, since the sintered body is porous, it has sufficient water-holding and air-ventilating abilities to promote growth of plants effectively. A bone material component is mainly composed of calcium phosphate or calcium phosphate from the composed additivexe2x80x94it is hardly dissolved by water but such can be dissolved by organic acids secreted from roots of plants.
Fertilizer components are generally absorbed to plants together with water. A component supplied from the bone material being held in the sintered body, or calcium phosphate supplied from the additive mainly composed of calcium phosphate can be dissolved by organic acids to form nourishing water. The nourishing water can be easily held in pores of the sintered body and hardly escapes from the pores of plant-cultivating artificial material Also, having sufficient hardness to provide a strong structure, the sintered body constituting the plant-cultivating artificial material can hold the nourishing water throughout a long term.
In a second aspect of the present invention, a plant-cultivating artificial material comprises: (1) a porous sintered body containing at least one of silica and alumina as a major component; (2) a substance mainly composed of a bone material component or calcium phosphate being held in the porous sintered body; and (3) a nitric acid component being held in the porous sintered body.
In the second aspect of the present invention, since the sintered body is porous, it has sufficient water-holding and air-ventilating abilities to promote growth of plants effectively. A bone material component is mainly composed of calcium phosphate or calcium phosphate from the composed additivexe2x80x94it is hardly dissolved by water but such can be easily dissolved by organic adds secreted from roots of plants to form a nourishing water. Also, such can be easily dissolved by nitric acid solutions to form a nourishing water when the nitric add component is dissolved by water to form nitric acid solutions. This nourishing water is easily held in pores of the sintered body to hardly escape from the pores of the plant-cultivating artificial material. Also, the sintered body constituting the plant-cultivating artificial material can hold the nourishing water throughout a long term having a hardness to hardly be broken.
A third aspect of the present invention provides a moderate process for producing the plant-cultivating artificial material described in the first aspect. In the third aspect of the present invention, a process for producing a plant-cultivating artificial material comprises the steps of (1) preparing a base material containing at least one of silica and alumina as a major component and having a powder or granular shape, and preparing a mixing substance mainly composed of at least one of bone material and an additive, the bone material containing calcium phosphate and gathered from an organism, the additive mainly composed of calcium phosphate; (2) mixing the base material with the mixing substance to obtain a mixture, and forming a green body by the mixture; and (3) heating the green body in a heated atmosphere to obtain a porous sintered body so that it can hold the bone material component supplied from the bone material or to hold calcium phosphate supplied from the additive in the porous sintered body, thereby obtaining a plant-cultivating artificial material.
In the third aspect of the present invention, the porous sintered body can hold a bone material component supplied from the organism, or can hold calcium phosphate supplied from the additive mainly composed of calcium phosphate. In particular, the bone material component or calcium phosphate can be held not only in the surface layer of the sintered body but also inside the sintered body. Accordingly, when the bone material component or calcium phosphate is dissolved by the organic acids from roots of plants to form a nourishing water, this nourishing water is easily held in pores of the sintered body to hardly escape from the pores of the plant-cultivating artificial material. Thus, the sintered body can hold the nourishing water throughout a long term because of the strong structure provided by sufficient hardness having a hardness to hardly be broken.
A fourth aspect of the present invention provides a moderate process for producing the plant-cultivating artificial material of the second aspect. In the fourth aspect of the present invention, a process for producing a plant-cultivating artificial material comprises the steps of: (1) preparing a base material containing at least one of silica and alumina as a major component and having a powder or granular shape, and preparing a mixing substance mainly composed of at least one of bone material and an additive, the bone material containing calcium phosphate and gathered from an organism, the additive mainly composed of calcium phosphate; (2) mixing the base material with the mixing substance to obtain a mixture, and forming a green body by the mixture; (3) heating the green body in a heated atmosphere to sinter a porous sintered body to hold a bone material component from the bone material or to hold calcium phosphate from the additive in the porous sintered body; and (4) bringing the porous sintered body into contact with a liquid including a nitric add component thereby holding the nitric acid component in the sintered body, and thereby constituting a plant-cultivating artificial material.
In the fourth aspect of the present invention, the porous sintered body can hold the nitric acid component, besides the bone material component and calcium phosphate. In particular, the nitric add component, the bone material component, and calcium phosphate can be held not only in the surface layer of the sintered body but also inside the sintered body.
The nitric add is dissolved by water to form the nitric acid solution. The bone material component supplied from the bone material being held on the sintered body, or calcium phosphate supplied from the additive mainly composed of calcium phosphatexe2x80x94such can be dissolved by the organic acids or by the nitric acid solution so as to form nourishing water. This nourishing water is easily held in pores of the sintered body to hardly escape from the pores of the plant-cultivating artificial material. Also, having a hardness to hardly be broken, the sintered body constituting the plant-cultivating artificial material can hold the nourishing water throughout a long term.
In the first and second aspects of the present invention, since the sintered body is porous, it sufficiently has a water-holding ability and an air-ventilating ability to promote growth of plants. The bone material component supplied from the bone material, or calcium phosphate supplied from the additive mainly composed of calcium phosphatexe2x80x94such can be hardly dissolved by water; such can be dissolved by organic adds secreted from roots of plants. The nourishing water including such is easily held in pores of the sintered body. Hence, the nourishing water hardly escapes from the pores of the plant-cultivating artificial material. So, the plant-cultivating artificial material can advantageously be used as a fertilizer to promote growth of plants.
Also, the sintered body constituting the plant-cultivating artificial material, having a sufficient hardness. So, the sintered body maintains nicely and holds the nourishing water containing the bone material components or calcium phosphate for a long time.
In the second aspect of the present invention, since the plant-cultivating artificial material holds the nitric add component, besides the bone material component supplied from the bone material, or besides calcium phosphate supplied from the additive composed of calcium phosphate. The nourishing water includes the nitric acid component besides the bone material component or calcium phosphate. This nourishing water is easily held in pores of the sintered body; so, it hardly escapes from pores of the plant-cultivating artificial material. Thus, the plant-cultivating artificial material can advantageously be used as a fertilizer to promote growth of plants.
In the third aspect of the present invention, the porous sintered body can hold the bone material component supplied from the organism or calcium phosphate supplied from the additive mainly composed of calcium phosphate. In particular, the bone material component or calcium phosphate can be held not only in the surface layer of the sintered body but also inside the sintered body. When the bone material component or calcium phosphate is dissolved by the organic acids secreted from roots of plants to form the nourishing water, this nourishing water is easily held in the pores of the sintered body and hardly escapes from the pores of plant-cultivating artificial material. Thus, the plant-cultivating artificial material can advantageously be used as a fertilizer to promote growth of plants. The plant-cultivating artificial material can hold the nourishing water throughout a long term, since it has a hardness to hardly be broken.
In the fourth aspect of the present invention, the porous sintered body can hold the nitric acid component besides the bone material component and calcium phosphate. In particular, not only in the surface layer of the sintered body but also inside the sintered body can hold these easily.
When the nitric add component is dissolved by water to form a nitric add solution, or when the bone material component or calcium phosphate is dissolved by the organic add or by the nitric add solution, the nourishing water containing such is easily held in the pores of the sintered body to hardly escape from the pores of the plant-cultivating artificial material. Therefore, the plant-cultivating artificial material can advantageously be used as a fertilizer to promote growth of plants. Also, the sintered body constituting the plant-cultivating artificial material can hold the nourishing water throughout a long term, since it has a hardness to hardly be broken.
According to the plant-cultivating artificial material of the present invention, the sintered body contains at least one of silica and alumina as a major component Therefore, the sintered body may contain only one or both of silica and alumina as a major component. Further, the sintered body may contain at least one of magnesium oxide, iron oxide, manganese oxide, sodium oxide, potassium oxide, etc.
The sintered body concerning the present invention is porous, having a plurality of pores. Porosity rate, pore-distribution, and average pore diameter in the sintered body affect the water-holding ability, the water-conducting ability, the air-ventilating ability, and the breeding condition of microorganisms; they may be chosen depending on the kind of base material and usage of the plant-cultivating artificial material. The base material may sometimes include burning substances. The burning substance may be organic substances, activated carbon coal powder, etc. Varying size and distribution of the burning substances, the bone material or the additives mainly composed of calcium phosphate, so it will adjust a pore diameter and a distribution of pore diameter in the sintered body. The reason is that the burning substances are burnt and lost to form pores. Also, parts of the bone material are melted or burnt to form pores. The pore is preferably a continued pore in comparison with an isolated pore.
As for the porosity rate of the sintered body, the upper limit may be set, for example, at 80%, 70%, 60%, 50%, 40%, or 30% by volume ratio; the lower limit can be set for example, at 5%, 10%, 15%, 20%, 30%, or 40%. The upper limit and the lower limit are not limited to these. Therefore, the porosity rate of the sintered body may be set, for example, in a range of 5%-80%, or in a range of 10%-70% at volume ratio. An increase of the porosity rate generally improves the water-holding ability, the water-conducting ability, and the air-ventilating ability, although it decreases hardness of the plant-cultivating artificial material.
As for the pore distribution of the sintered body, the upper limit may be set for example, at 3 mm, 2 mm, 1 mm, 500 xcexcm, 200 xcexcm, 100 xcexcm, 50 xcexcm, or 30 xcexcm; the lower limit may be set, for example, at 0.01 xcexcm, 0.1 xcexcm, 0.5 xcexcm, 1 xcexcm, 5 xcexcm, 10 xcexcm, or 20 xcexcm. The upper limit and the lower limit of the pore distribution are not limited to these. The pore distribution of the sintered body can be set for example, in a range of 0.01 xcexcm-3 mm, in a range of 0.1 xcexcm-1 mm, or in a range of 1 xcexcm-500 xcexcm As for the average diameter of the pore of sintered body, the upper limit may be set, for example, at 3 mm, 1 mm, 500 xcexcm, 200 xcexcm, 100 xcexcm, or 50 xcexcm; the lower limit may be, for example, at 0.01 xcexcm, 0.1 xcexcm, 0.5 xcexcm, 1 xcexcm, or 10 xcexcm. The upper limit and the lower limit are not limited to these. The average diameter concerning the pore of the sintered body is set, for example, in a range of 0.01 xcexcm-3 mm, in a range of 0.1 xcexcm-1 mm, or in a range of 1 xcexcm-500 xcexcm. The average diameter may be defined as a mode diameter which means the most frequent diameter, or as a median diameter which means the middle value between the upper limit and the lower limit.
The sintered body may have a plurality of peaks showing a frequency of pore diameter in pore-distribution. The number of peaks may be three or two. In the case where the burning substance and the bone material are mixed with the base material, the difference between the burning substance and the bone material in powder-diameter will provide a plurality of peaks showing a frequency of pore-diameter in the sintered body.
The total amount of Ca (calcium) and P (phosphorus) may be varied depending on usage of the plant-cultivating artificial material, etc. According to a preferable mode, the total amount of Ca (calcium) and P (phosphorus) may be set in a range of 3%-50% in weight ratio, when the plant-cultivating artificial material is set to be 100%.
As for the total amount of the above mentioned Ca (calcium) and P (phosphorus), the lower limit may be, for example, 5% or 7% in weight ratio; the upper limit may be, for example, 45%, 40%, 35%, 30%, or 25% in weight ratio. The upper limit and the lower limit are not limited to these. The bone material in a preparing step may be in a raw state, in a heated state with steam, or in a burned state.
According to the second aspect of the present invention, the sintered body holds the nitric acid component It generally is held having NO3xe2x88x92 ion The amount of the nitric acid component, NO3xe2x88x92 ion, being held in the sintered body, can be decided depending on situations of the pore, applications of the plant-cultivating artificial material, etc. According to the preferable mode, as for the amount of NO3xe2x88x92 ion, the lower limit may be set, for example, at 0.2%, 0.5%, 1%, or 5% by weight ratio; the upper limit may be set for example, at 9%, 10%, 13%, 15%, or 30% by weight ratio, when the plant-cultivating artificial material is set to be 100%. The lower limit and the upper limit are not limited to these. Therefore, the amount of NO3xe2x88x92 ion may be, for example, in a range of 0.2%-30%, in a range of 0.2%-15%, or in a range of 1%-10% by weight ratio.
The third aspect of the present invention provides a moderate process for producing the plant-cultivating artificial material holding the bone material component. According to the third aspect of the present inventionxe2x80x94the mixing and forming stepxe2x80x94It is to mix the base material containing at least one of silica and alumina as a major component which has a powder form or granular shape with the mixing substance that is mainly composed of at least one of bone material and the additive. In this mixture, a mixing rate and a kind of the base material can be chosen depending on a required amount of bone material, a required amount of calcium phosphate, types of plant to be grown, etc.
For example, the mixing rates of volume are as follows:
(base material:bone material )=(20: 80)-(95: 5) in particular,
(base material:bone material )=(40: 60)-(80: 20)
The mixing ratio may be set to be the same range between the base material and the additive.
The mixing and forming step permits a kneading machine to be used. In the mixing and forming step, it is desirable to also add water for efficient kneading. The base material may be wastes being scrapped in factories or in scrapping fields such as casting foundries. The wastes may be dust-wastes, sludge-wastes. Dust wastes may be collected by dust collectors. The average particle size of the dust-wastes may be roughly in a range of 1 xcexcm-200 xcexcm, or in a range of 3 xcexcm-50 xcexcm. The sludge wastes may be sludge in sewerage of factories such as casting foundries. The sludge wastes may be sludge precipitated in tanks for storing liquidus wastes, etc. Generally, the sludge particle is smaller than the dust particle in average particle size.
The additive mainly composed of calcium phosphate to be used in the present process means either artificial products made of calcium phosphate itself or artificial products containing calcium phosphate as a major component.
The bone material in a preparing step, as described above, may be in a raw state, in a heated state with steam, or in a burned state. The bone material may be selected from beasts, fishes, and so on. The beast may be at least one selected from the group including cattle, horses, sheep, chickens, and so on. The bone material generally contains calcium phosphate as a main component, sometimes including protein. The bone material may be crushed to form a powder shape, a granular shape, or a shard shape, depending on applications of the plant-cultivating artificial material, etc. The size of the base material, the size of the bone material, and the distribution of size thereofxe2x80x94such affects pore size of the sintered body constituting the plant-cultivating artificial material. The pore of the sintered body generally increases in size when the base material, the powder of the bone material, and calcium phosphate are large in size. The pore of the sintered body decreases in size when the base material, the bone material powder, and calcium phosphate are small in size.
In the mixing and forming step, the green body is formed in a predetermined shape. The green body may be in a granular shape or in a pellet shape, and it may sometimes be in a block shape. In the mixing and forming step, the green body may have a granular shape or a pellet shape by means of frictional forces caused by stirring blades. The green body may have a granular shape or a pellet shape by use of forming dies for compression. Also, the green body may be formed in a cylinder shape or in a rough cylinder shape by cutting a continued rod in series in a length direction thereof The continued rod may be obtained by the extrusion method.
In the heating step, the green body is heated in a heated atmosphere to form a porous sintered body so as to produce the plant-cultivating artificial material. The heating temperature can be varied depending on size and composition of the green body, existence of a baking auxiliary, strength being requested as the plant-cultivating artificial material, etc. As for the heating temperature, the lower limit may be set, for example, at 400xc2x0 C., 500xc2x0 C., 600xc2x0 C., 700xc2x0 C., 800xc2x0 C., or 900xc2x0 C.; the upper limit may be set, for example, at 1300xc2x0 C., 1200xc2x0 C, 1100xc2x0 C., 1000xc2x0 C, or 900xc2x0 C. The upper limit and the lower limit of the heating temperature are not limited to these. Therefore, the heating temperature may be in a range of 400xc2x0 C.-1300xc2x0 C., in a range of 500xc2x0 C.-1200xc2x0 C., or in a range of 700xc2x0 C.-1100xc2x0 C.
When the green body is sintered, it is hardened to form the sintered body and hardly be broken. The heating time is chosen depending on heating temperature, size of the green body, and hardness being requested as the plant-cultivating artificial material. So, the heating time may be, for example, in a range of 10 minutes-10 hours, in a range of 20 minutes-5 hours, or in a range of 1 hour-2 hours. The heating time is not limited to these. In the case where the bone material contains protein and the like, it is assumed that parts or all of protein is lost during the burning process.
Average size of the plant-cultivating artificial material can be varied depending on applications thereof. As for the average size, the lower limit may be set, for example, at 50 xcexcm, 200 xcexcm, 1 mm, or 2 mm; the upper limit may be set, for example, at 50 mm, 20 mm, 15 mm, 10 mm, 3 mm, or 1 mm. The upper limit and the lower limit of the average size are not limited to these. Therefore, the average size of the plant-cultivating artificial material may be, for example, in a range of 50 xcexcm-50 mm, in a range of 200 xcexcm-20 mm, or in a range of 1 mm-15 mm.
The process of the fourth aspect provides a moderate process for producing the plant-cultivating artificial material holding the nitric add component besides a bone material component supplied from the bone material, or besides calcium phosphate supplied from the additives mainly composed of calcium phosphate. The process of fourth aspect is basically similar to that of the third aspect in the mixing, forming and heating steps. The difference between the fourth aspect and the third aspect is as follows:
After the porous sintered body is formed by sintering in the heating step, the sintered body is brought into contact with liquid including the nitric acid component This allows the nitric acid component to infiltrate into the pores of the sintered body. Further, this allows the nitric acid component to be held in pores of the sintered body. The liquid including the nitric acid component may be nitric acid aqueous solutions. Also, when the sintered body is brought into contact with the liquid including the nitric acid component, parts of the bone material component of the sintered body are dissolved by the liquid so as to form pores; accordingly, the plant-cultivating artificial material increases in porosity rate.
The concentration of the nitric acid in the liquid can be chosen depending on the target amount of nitric add component to be held in the sintered body. The held amount of the nitric acid component generally is increased in the sintered body, when the concentration of nitric acid is higher in the liquid. As for the concentration of the nitric acid in the liquid, the upper limit may be set, for example, at 20N, 10N, 5N, 3N, or 1N; the lower limit may be set for example, at 0.01N, 0.1N, 0.5N, or 1N. The upper and lower limits of concentrations of the nitric acid component are not limited to these. The term of xe2x80x9cN xe2x80x9d herein means normality.
In bringing the sintered body into contact with the liquid including the nitric acid component, the sintered body may be soaked in the liquid, or the liquid may be sprayed to the sintered body.
In the fourth aspect of the present invention, the porous sintered body can hold the nitric add component, besides the bone material component supplied from the bone material, or besides calcium phosphate supplied from the additive. In particular, not only the surface layer of the sintered body but also the inside of the sintered body can hold these. When the nitric add component is dissolved by water to form nitric add solutions, the bone material components or calcium phosphate is dissolved by the organic adds or by the nitric add solutions so as to form the nourishing water, the nourishing water is easily held in the pores of the sintered body and hardly escapes from the pores of the plant-cultivating artificial material.
The plant-cultivating artificial material may be used as a soil-improving material to be buried in soil, or it may be used together with a nourishing solution without being buried in soil.